If you are into CTF, you will know your paddock has two distinctly different soil conditions – loose and friable for growing crops, and hard and compacted for driving on. You will also realise that each area requires different management. A successful CTF system is more than just getting the wheels in the right place.
To a large extent, your cropping soil will look after itself once you keep the wheels off it. However, managing wheel tracks is very important and introduces some civil engineering to your farming enterprise.
The ideal CTF wheel track is hard, dry and wide enough to support wheels without sliding off. In vegetable production, wheel tracks tend to be narrow to maximize the crop area and are often wet, either from rainfall or irrigation. A wet wheel track may be greasy and hard to stay on, but an underwater wheel track will have lost a lot of its strength. This can lead to deep ruts from essential passes, such as from unavoidable harvest traffic.
So what to do about it, and do I have all the answers? No, I don’t have all the answers – but here are some ideas, some based on experience, others as yet untried.
First and foremost; correct paddock layout and effective surface drainage are essential to good wheel track performance. Some slope (and farming above sea level!) is a good start. Wheel tracks should run up and down slope for positive drainage. In undulating topography, there are probably places where you travel across slope to some degree, but positive drainage is the key. Strategic drainage might be necessary if there are low spots in the paddock. Upslope diversion drains to prevent run-on, and down slope drains to collect run-off, are key elements. These should take water away as fast as possible, and may be broad-based and grassed so they can be driven over. They may be incorporated into paddock headlands.
Flat (or very low slope) paddocks present particular challenges. Laser grading may be an option. Consider laser grading just the base of the wheel track. The bed height may vary a little, so you will have to judge what is acceptable.
Will this solve all your problems? Probably not. Track erosion is one potential issue, depending on slope, although with improved infiltration in the bed, there should be a lot less water running down the tracks.
Daily harvest pressures for fresh produce are a challenge. You don’t always have the freedom to wait for tracks to dry, but at least if they are drained, they will regain their strength faster. Greasy tracks test the system – steerage discs on tractors and other equipment may help.
Despite your best efforts, there will be times when it all turns to custard. Maintenance of wheel tracks will be part of your CTF work program. After all, they are roads, and roads need maintenance. And it’s a fair bet you will spend less time maintaining them, than you would otherwise spend cultivating.
Pictures: Trafficability impacts on a heavy clay soil after rain (lots of it – 150 mm in 2 days).
This is a conventional tillage area 2 days after rain
And here, a well drained CTF wheel track 2 days after rain
John is a Controlled Traffic Farming researcher at the Tasmanian Institute of Agricultural Research and the Department of Primary Industries.